Karren Brady at West Ham United's ground in east London. She has been a Tory party member for more than a decade. Photograph: David Ashdown /Rex

She is known as the first lady of football but last week proved that Karren Brady has moved beyond her role as the game's senior female wheeler dealer. David Cameron unveiled the vice-chairman of West Ham United FC as the Conservatives' small business ambassador. Brady returned the compliment by introducing the chancellor, George Osborne, for his keynote speech at the Tory conference in Manchester, as "the right man with the right plan".

Brady has supported the Conservatives since she was 18, during the heyday of the Thatcher government, and has been a party member for more than a decade. It was no secret that she was sympathetic to the party but this was her first foray from the world of sports and business into politics.

Brady is 44 but has been among the UK's most high-profile businesswomen for more than 20 years. She became managing director of Birmingham City at 23 when the club was bought by David Sullivan and David Gold, business partners who had made their fortunes in the pornography industry.

Sullivan had spotted Brady when she sold him advertising at London's LBC radio station and hired her to work at his Sunday Sport tabloid newspaper.

Before LBC, aged just 18, Brady had muscled her way onto the graduate trainee scheme at Saatchi & Saatchi without having gone to university.

At Birmingham FC she proved herself a tough operator. The club had big debts and was in administration when Sullivan and Gold bought it in 1993 – but in her first year in charge Birmingham made its first ever trading profit.

She also had to contend with sexism verging on misogyny in a game that was even more macho than it is now – but she had the charisma to deal with it.

At this time a Birmingham player quipped: "I can see your tits in that shirt." Brady replied: "When I sell you to Crewe, you won't be able to see them from there will you?" She sold him.

Brady's leadership and Sullivan and Gold's money took Birmingham back to English football's top flight with promotion to the Premier League in 2001. There she made an immediate impact on the Premier League by persuading its clubs to allow a limited number of players to go out on loan to rivals – against the wishes of the league's management.

Brady used her position as the league's only female chief executive to her advantage, according to a source who saw her operate at the time: "She can be very charming with blokes of a certain age and, though I hesitate to say it, vaguely coquettish." But aside from charm, a recurring theme in the Brady story is that she did her homework.

"She worked out why player loans would make sense for every kind of club – whether it was the top tier, with expensive assets not getting a game, or the lower tier like Birmingham who needed players but didn't want to risk paying transfer fees. She lobbied over dinner and at the bar and got people like Arsenal's David Dein and Manchester United's Peter Kenyon onside when you might have expected them to say no."

This thoroughness runs through all accounts of Brady in operation. She is said to have called people she knew at the Treasury to find out about George Osborne before deciding to accept his offer to be the Tories' business tsar. Their loyalty to the chancellor persuaded her to take the plunge.

Sullivan and Gold sold their stakes in Birmingham in 2009 and the following year bought West Ham – just a few miles east of Edmonton, where Brady was brought up in affluence by her millionaire Irish entrepreneur father Terry and her Italian mother, Rita.

Brady was installed as vice-chairman of West Ham and her return to London made her even more visible.

Brady, who is married to a former Birmingham City footballer and has two teenage children, had been building her profile outside football for some time, writing novels, winning awards, being named among the country's most powerful women and appearing on the BBC's Desert Island Discs in 2007.

But it was her role on BBC1's The Apprentice that year that transformed Brady from a businesswoman into a national brand. After grilling finalists at the end of earlier series, she became Lord Sugar's female aide, observing and reporting back on the hapless business wannabes' travails in seeking to work for the Labour peer.

Stuart Baggs, a contestant in Brady's first series who claimed to be "the brand", says her empathetic exterior masked coldness and he questioned her claims to represent women in business.

"She feels that because she is a woman she has battled more than the rest of us. You can't detract from her achievements but who has voted for her to be a spokeswoman for all women?"

Baggs claims a female contestant who was coping badly with the show stresses asked to have a quiet word with Brady, but she bluntly refused. It is, however, an allegation dismissed as an "absolute lie" by someone who knows Brady well.

Tom Gearing, runner-up in last year's contest, tells a different story. Fellow contestant Katie Wright was ill one day and wanted to go home sick.

"Karren took Katie to one side and said, 'I know you're feeling ill but this is a great opportunity and you've got to fight through this because you can't afford to have a sick day on The Apprentice. You might get fired.' It was quite surprising at the time because she'd been quite distant in her observer role, but after that we got to know her better."

What does it mean to be the Tories' small business ambassador? Not even Brady knows yet, which is why she has turned down interviews. In typical fashion she wants to keep a low profile until she has worked out how to make her mark and avoid the criticism aimed at Mary Portas, the retail guru lured by Cameron to revive the UK's high streets with mixed results. Unlike Portas, Brady will be working for the Conservative party, not the coalition.

Brady refers to herself as a "fair Conservative" – meaning the state should encourage and free entrepreneurs to succeed while providing support such as healthcare when they are in need.

Her charity work combines campaigning for women and health issues. She is an ambassador for Wellbeing of Women, which raises funds for gynaecological research; Wellchild, which supports families of seriously ill children; and the Stroke Association.

Her work with the Stroke Association is poignant. She came close to death in 2006 when an aneurysm was discovered in her brain. She came through invasive neurosurgery but remains at high risk of having a stroke in later life.

Brady supports the charity by chairing its awards for people who have rebuilt their lives after a stroke, hosting other events and introducing her network of wealthy contacts to the association. On Wednesday this week she spoke at a 300-strong gala dinner of rich philanthropists, part of a programme that raises £2m a year.

Stroke Association fundraiser John Harvey said: "This was one of the biggest weeks of this stage of her life but she was here with us and she spoke from the heart about what we do."

But there is that rigorous research again. Brady scrutinises the charity's annual report and holds staff to high standards, Harvey said. "There are a lot of people who jump on the bandwagon with this sort of thing but she is very careful about what she associates herself with."

Some may be surprised that such a cautious, selective operator should put her reputation on the line by entering politics and attaching herself to the Tories when the chancellor's austerity measures are dividing the country.

There are rumours of Brady standing as the Tory candidate for London mayor in 2016 when Boris Johnson's second term is complete.

However, the timing might not work out. Brady will still be working to transform the Olympic Stadium for West Ham after winning the battle with Tottenham Hotspur to secure the site at Stratford.

But if she stood for election, the woman Harvey describes as "a force of nature" could shake up politics – just as she did football more than 20 years ago.

Potted profile

Family Married the Canadian footballer Paul Peschisolido in 1995 after he played for Birmingham. Two children: Sophia, 17, and Paolo, 15.

Career Joined Saatchi & Saatchi aged 18 and moved to London Broadcasting Corporation a year later. Moved to David Sullivan's Sport Newspapers and became a director aged 20. Made managing director of Birmingham City FC in 1993. Became vice-chairman of West Ham FC in 2010. She is a non-executive director of Sir Philip Green's Arcadia group and a consultant to Simon Cowell's Syco.

High point Winning the long and bitter battle with Tottenham Hotspur for West Ham to take over the London Olympic stadium earlier this year.

Low point Arrested and questioned by City of London police in 2008 as part of an investigation into corruption in football. Brady denied any wrongdoing and no charges were brought.

What she says "It is this government that stands by you, it is this government that understands that without small businesses Britain would not be what it is today."

What they say "Cameron and Osborne should offer her a seat in the Lords. She will contribute" – Labour peer Lord Sugar via Twitter.

"When you meet her, she comes across as a very strong businesswoman. She had a really commanding presence and when she spoke people would listen" - Tom Gearing, Apprentice 2012 runner-up.